The conveyance of information or data in electronic form generally falls into four unique categories: (1) photonic, where the information is conveyed by a modulated stream of photons, transported by a solid physical medium, as exemplified by fiber optic communication systems; (2) photonic, where the information is conveyed by a modulated stream of photons, transported through free space or air as exemplified by radio communication systems; (3) electronic, where the information is conveyed by a modulated stream of electrons in a solid physical media, such as a wire or silicon chip; and (4) electronic, where the information is conveyed by a modulated stream of electrons traveling through free space.
Fundamental to any computer or communications system is the conveyance of information between particular sources and destinations. Devices generally known as switches direct the data flow between particular input and output ports. Well-known techniques can be used to design switches adapted to the four classes of data conveyance mentioned above.
One technique for photonic data switching involves the use of a laser whose frequency or color can be adjusted. This adjustability combined with a prism-like device that translates color change into spatial direction change allows a laser beam to be redirected in lockstep with the frequency of the laser. By changing direction, a beam can be steered to a particular output port amongst an array of ports spatially offset from one another. Although this technique holds the promise of high-speed switching, it has not yet been adapted to scan a large number of output ports.
Another method of switching photonic data is known as microelectromechanical system (MEMS)-based movable mirror switches. Movable mirrors direct data-modulated laser beams to particular output ports. Even the tiniest of MEMS mirrors has tangible mass and needs to physically move to redirect the beam. These two facts limit the switching speed of any MEMS technique to the point that the technology is best suited as a reconfigurable patch panel rather than a packet by packet data switch.
Another technique for packet switching at radio frequencies involves the use of phased antenna arrays to steer the direction of the radio signal. At millimeter wavelengths, these phased array antennas can be acceptably small, but supporting a large number of ports using such antennas requires a complex phased antenna array.
Another method of electronic switching uses single-stage crossbars. A crossbar is a semiconductor-based logic device that is used for switching. The main disadvantage of single-stage crossbars is scalability: the number of internal components in a crossbar increases exponentially or nearly exponentially as the number of ports increases.
Crossbars are also limited by crosstalk. As the number of crossbar switches increases, the unwanted coupling from individual switches in the off state increases. Crosstalk limits the maximum size of a crossbar switch, since the increased crosstalk noise reduces the signal-to-noise ratio of the desired signal.
The Batcher Banyan tree architecture is an interconnection topology that allows smaller crossbars to be combined hierarchically to form a larger, higher port count switch. The Batcher Banyan tree architecture reduces the number of switching elements relative to a flat hierarchy, but increases the number of stages in the hierarchy and thereby increases the latency compared to a flat hierarchy.
As described above, these and other various prior art switching techniques have a variety of disadvantages. What is needed, therefore, are improved switching techniques which overcome the disadvantages of the prior art.